Light Scanning Apparatus Motor Control for Deviation Measurement
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Solution Overview
Problem
In light scanning apparatuses with rotary polygon mirrors, measuring the deviation of starting positions for two scanning lines can disrupt the constant rotation speed, leading to image quality deterioration due to the temporary shutdown of one light beam and differing detection cycles for the two beams.
Innovation Solution
A light scanning apparatus with a motor control unit that adjusts rotation based on the second detection timing during measurement periods and uses a predetermined cycle during non-measurement periods, ensuring the rotary polygon mirror maintains constant speed by decoupling rotation control from the first detection timing used for deviation measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If one light beam is temporarily turned off to measure deviation amount, then deviation measurement capability is improved, but constant rotation speed of rotary polygon mirror cannot be maintained
Solution Approach 1:
The patent segments the light beams into two independent channels (first light beam for rotation control, second light beam for deviation measurement). By separating the functions assigned to different light beams, the system can measure deviation using the second beam while maintaining constant rotation speed control through the first beam, resolving the contradiction between measurement capability and speed stability.
Solution Approach 2:
The patent introduces an intermediary mechanism where the detection timing of the first light beam serves as a reference signal for the rotation control, while the second light beam provides the deviation measurement. This intermediary reference allows the system to decouple the rotation control from the deviation measurement process, enabling both functions to operate independently without interfering with each other.
2Speed
If detection timing of first light beam is used for rotation control, then rotation speed control is improved, but accurate deviation measurement becomes difficult
Solution Approach 1:
The patent assigns different functional roles to different light beams: the first light beam is dedicated to rotation speed control, while the second light beam is dedicated to deviation measurement. This functional segmentation eliminates the conflict where using the first beam's detection timing for control would interfere with accurate deviation measurement.
Solution Approach 2:
The patent uses the detection timing information of the first light beam as a reference copy for synchronization, while the second light beam provides the actual deviation measurement data. This copying approach allows the system to maintain rotation control accuracy without using the same detection timing for deviation measurement.
3Measurement precision
If multi-beam laser scanning apparatus selectively lights up light beams to measure deviation, then deviation measurement capability is improved, but image quality deteriorates due to scanning line alignment errors
Solution Approach 1:
The patent segments the measurement process into two independent parts: rotation control based on the first light beam and deviation measurement based on the second light beam. This segmentation allows deviation measurement without disrupting the rotation control, thereby preventing scanning line alignment errors and maintaining image quality.
Solution Approach 2:
The patent implements a feedback mechanism where the deviation measured by the second light beam is used to correct the starting positions of scanning lines, while the first light beam continues to provide real-time feedback for rotation speed control. This dual feedback system ensures both accurate deviation measurement and maintained scanning line alignment.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows the rotary polygon mirror to maintain constant speed during deviation measurement, preventing image quality deterioration and ensuring accurate scanning line alignment.
Implementation Method 1
a rotary polygon mirror configured to be rotated by the motor, periodically deflect the first light beam and the second light beam emitted from the light emission unit and form two scanning lines on a scan object
Implementation Method 2
an optical sensor configured to detect the first light beam and the second light beam deflected by the rotary polygon mirror
Data Source
AI summary
A light scanning apparatus includes: a light emission unit emitting a first light beam and a second light beam; a motor; a rotary polygon mirror rotated by the motor, forming two scanning lines on a scan object at the same time; an optical sensor detecting the first light beam and the second light beam deflected by the rotary polygon mirror; a deviation measurement unit measuring a deviation amount of starting positions of the two scanning lines on the scan object based on a first detection timing at which the optical sensor detects the first light beam and a second detection timing at which the optical sensor detects the second light beam; and a motor control unit controlling rotation of the motor based on the second detection timing in a measurement non-execution period, and controls rotation of the motor without using the first detection timing in a measurement execution period.